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How to change my code to make it more efficient?

in this code is playing Rock Paper Scissors, between the computer and the user. My code is all working great, however, I'm trying to think of a better way to make it ask the user if they would want to play again. If yes, then it would start the program again, if no, then it would stop. My "yes" seems to work but the no will stop and not go through all the way. Any suggestions or tips on how to do this? I will trying to incorporate a different while loop, but wasn't working. Would a do loop be good for this scenario? Thanks!
//import scanner
import java.util.Scanner;
import java.util.*;
//declare variables and main methods
class Rock {
Scanner scan = new Scanner(System.in);
Random generator = new Random();
String response, name;
char choice;
int rounds, computerChoice, userScore, computerScore;
boolean playIntro = true;
boolean playGame = true;
//this method will run the entire progrma
public void playRPS(){
//while loop for beginning of game
while(playIntro){
System.out.println("This is a game of Rock Paper Scissors!");
System.out.println("Please enter your name: ");
name = scan.nextLine();
//while loop for the actual part of the game
while(playGame){
System.out.println("Type R (Rock), P (Paper), or S (Scissors): ");
choice = scan.nextLine().charAt(0);
computerChoice = generator.nextInt(3)+1;
//using switch and case for each choice
switch (choice){
//case for Rock
case 'R':
if(computerChoice==1){
System.out.println("Tie between you and the computer! Go again.");
break;
}
else{
if(computerChoice==2){
System.out.println("The computer beat you this round");
computerScore++;
break;
}
else{
System.out.println("You won this round");
userScore++;
break;
}
}
//case for Paper
case 'P':
if(computerChoice==2){
System.out.println("Tie between you and the computer! Go again.");
break;
}
else{
if(computerChoice==3){
System.out.println("The computer beat you this round");
computerScore++;
break;
}
else{
System.out.println("You won this round");
userScore++;
break;
}
}
//case for Scissors
case 'S':
if(computerChoice==3){
System.out.println("Tie between you and the computer! Go again.");
break;
}
else{
if(computerChoice==1){
System.out.println("The computer beat you this round");
computerScore++;
break;
}
else{
System.out.println("You won this round");
userScore++;
break;
}
}
}
System.out.println("You have "+userScore+" points and the computer has "+computerScore+" points");
if (userScore==5){
System.out.println("\nOut of 5 rounds, You beat the computer!");
playGame = false;
}
else if (computerScore==5){
System.out.println("\nOut of 5 rounds, The computer beat you.");
playGame = false;
}
}
askUser();
}
}
public void askUser(){
System.out.println("\nDo you want to play this Rock Paper Scissors again? Type yes: ");
response = scan.nextLine();
if (response.equalsIgnoreCase("yes")){
playGame = true;
userScore=0;
computerScore=0;
}
else{
playGame = false;
scan.nextLine();
}
}
public static void main() {
Rock prog = new Rock();
prog.playRPS();
}
}

I wouldn't say this is necessarily more efficient or even better but it is a little more concise. It's major elements are.
use Lambdas to decide the winner based on the chosen move.
use a map to call the proper Lambda based on the user's move. The lambda then evaluates the two moves to decide the outcome.
for simplicity, moves are selected by number
Of course, the important thing is that your code works.
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.Scanner;
import java.util.Set;
import java.util.function.Function;
public class RockPaperScissors {
final static int PAPER = 1;
final static int ROCK = 2;
final static int SCISSORS = 3;
// the next two declarations allows the previous three to take on any values.
private Set<Integer> allowedMoves = Set.of(PAPER, ROCK, SCISSORS);
private List<String> moves = List.of("PAPER", "ROCK", "SCISSORS");
private String ROCK_WINS_MSG = "Rock crushes scissors";
private String SCISSORS_WINS_MSG = "Scissors cuts paper";
private String PAPER_WINS_MSG = "Paper covers rock";
private String COMPUTER_WINS = ", computer wins!";
private String YOU_WIN = ", you win!";
private Function<Integer, String> CHECK_PAPER =
(c) -> c == PAPER ? "It's a tie!" :
c == ROCK ? PAPER_WINS_MSG + YOU_WIN :
SCISSORS_WINS_MSG + COMPUTER_WINS;
private Function<Integer, String> CHECK_ROCK =
(c) -> c == ROCK ? "It's a tie!" :
c == SCISSORS ? ROCK_WINS_MSG + YOU_WIN :
PAPER_WINS_MSG + COMPUTER_WINS;
private Function<Integer, String> CHECK_SCISSORS =
(c) -> c == SCISSORS ? "It's a tie!" :
c == PAPER ? SCISSORS_WINS_MSG + YOU_WIN :
ROCK_WINS_MSG + COMPUTER_WINS;
private Map<Integer, Function<Integer, String>> evalUser =
Map.of(PAPER, CHECK_PAPER, ROCK, CHECK_ROCK, SCISSORS,
CHECK_SCISSORS);
public static void main(String[] args) {
new RockPaperScissors().play();
}
public void play() {
Random r = new Random();
Scanner scan = new Scanner(System.in);
while (true) {
System.out.printf("%n%d : %s%n%d : %s%n%d : %s%n%s%n",
PAPER, "PAPER", ROCK, "ROCK", SCISSORS,
"SCISSORS", "Any other integer to quit.");
System.out.print("Your move! ");
String str = scan.nextLine();
int move;
try {
move = Integer.parseInt(str);
if (!allowedMoves.contains(move)) {
break;
}
} catch (IllegalArgumentException ie) {
System.out.println("Only integers permitted.");
continue;
}
System.out.println("\nYou chose " + moves.get(move - 1));
int cmove = r.nextInt(3);
System.out.println(
"The computer chooses " + moves.get(cmove));
System.out.println(evalUser.get(move).apply(cmove + 1));
}
System.out.println("\nGame over!");
}
}
Once suggestion for your code would be to look at the switch cases. The code for each case is practically identical. I would look for similarities and make the evaluation a single method (something I didn't really do in my code). Then in each case, call that method with the appropriate arguments. One such argument would be either "computer" or "you" based on the context.

There's nothing that ever sets playIntro false, and therefore the outer loop will never terminate.
When askUser() sets playGame false the inner loop terminates, and you fall into the outer loop, which keeps on looping.
I don't see any reason for the outer loop to exist at all. You only want to print the introduction and ask the player's name once.
This isn't so much a matter of 'efficiency' as of correctness.
Incidentally, it would be better to make askUser() return a true/false value rather than set a member variable. Then you can use it directly in a 'while' expression.
The overall structure of playRPS() then looks like:
public void playRPS() {
... print intro, ask name ...
do {
... play one game ...
} while (askUser());
}

Java rock paper scissor printing the statements oddly

So here i am trying to create a program that takes an input as an int and then plays a game of Rock paper scissors. It seems to want to reprint statements that it shouldn't be and is skipping printing statements as well. I would love some assistance if possible. I have tried setting up print statements everywhere but it has just been more confusing.
import java.util.Scanner;
public class RPSS{
//Main method
public static void main(String[ ] argc)
{
System.out.println("Lets play rock paper scissors");
Scanner tnt = new Scanner(System.in);
String computerHand; // string variable for computer choice
String userHand; // string variable for user choice
//
String answer = "";
while (!a
nswer.equals("No") && (!answer.equals("no"))){
userHand = userHand();
computerHand = computerHand();
System.out.println("The User picks " + userHand + " " );
System.out.print("The Computer picks " + computerHand );
String winner = getWinner(computerHand, userHand);
System.out.println(winner);
System.out.println("play again?");
answer = tnt.next();
}
//Condition for the do-while loop
}
public static String userHand(){ //method for users choice in the game
//prints message to user giving them choices
System.out.println(" ");
System.out.println("1. Rock ");
System.out.println("2. Paper ");
System.out.println("3. Scissors ");
int userChoice; // user choice variable in this method
Scanner tnt = new Scanner(System.in); // creates instance of scanner class
userChoice = tnt.nextInt(); //reads user input
return getChoice(userChoice); //returns user choice to userChoice
}
public static String computerHand() //method for computer generated choice
{
int computernum = 1 + (int)(Math.random() * (( 2) +1));
return getChoice(computernum);
}
public static String getChoice(int num) //method recieving both computer hand and user hand
{
// if statements to place the correct choice
String choice = "";
if (num == 1){
choice = "Rock";
}
else if(num == 2){
choice = "Paper";
}
else if(num == 3){
choice = "Scissors";
}
return choice;
}
// Method determing the winner
public static String getWinner(String computerChoice, String userChoice)
{
computerChoice = computerHand(); //places computerChoice variable in computerhand
userChoice = userHand(); //does same for user choice
String winner="";
if (userChoice.equals("Rock") && computerChoice.equals("Paper")){
System.out.println("The computer wins");
return winner;
}
else if (userChoice.equals("Paper") && computerChoice.equals("Scissors")){
System.out.println(" The computer wins");
return winner;
}
else if (userChoice.equals("Scissors") && computerChoice.equals("Rock")){
System.out.println(" The computer wins ");
return winner;
}
else if (userChoice.equals("Rock") && computerChoice.equals("Paper")){
System.out.println(" The computer wins ");
return winner;
}
else if(userChoice.equals(computerChoice))
{
System.out.println(" There is no winner");
return " ";
}
else{
return winner;
}
}
}

The first problem is that userhand() and computerHand() are being called twice per "round", once at the beginning of the while loop inside the main method and once at the beginning of the getWinner() method. Elimination of the calls at the beginning of the getWinner() method should solve the repeats.
The 2nd Problem is that instead of modifying the value of winner inside the getWinner() method before returning it, you are you are simply outputting the message via println(). an example of fixing this would be converting this:
if (userChoice.equals("Rock") && computerChoice.equals("Paper"){
System.out.println("The computer wins");
return winner;
}
to this:
if (userChoice.equals("Rock") && computerChoice.equals("Paper")){
winner = "The computer wins";
return winner;
}
another minor issue is the fact that
userChoice.equals("Rock") && computerChoice.equals("Paper")
is checked twice, id just remove the entire if else block based around the
2nd check of it
Lastly i would treat the final else clause as the player wins one and set winner to something like " The player wins "

Java Do While isn't working properly

Sorry I am new to this site so not sure how this will show up. I am trying to make a simple Rock, Paper, Scissors game. After the while statement, if R, P, S isn't entered, the program just does nothing. I want it to loop back to the question at the beginning so a right choice can be entered. Also, how would I enter a print statement like "Invalid Choice Please Retry"?
package rps.gameapp;
import java.util.Scanner;
public class RPSGameApp
{
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
String userChoice;
String playAgain;
int randNum = (int) (Math.random() * 3);
do
{
System.out.println("Welcome to Rock, Paper, Scissors Game.");
System.out.println("Pick R, P, or S.");
userChoice = sc.nextLine();
while (!userChoice.equalsIgnoreCase("P")
&& !userChoice.equalsIgnoreCase("R")
&& !userChoice.equalsIgnoreCase("S"));
String compChoice = "";
switch (randNum)
{
case 0:
compChoice = "R";
break;
case 1:
compChoice = "P";
break;
case 2:
compChoice = "S";
break;
}
System.out.println("The computer entered \"" + compChoice + "\".");
if (compChoice.equalsIgnoreCase(userChoice))
{
System.out.println("Draw");
} else if (userChoice.equalsIgnoreCase(userChoice)
&& compChoice.equalsIgnoreCase("S")
|| userChoice.equalsIgnoreCase("P")
&& compChoice.equalsIgnoreCase("R")
|| userChoice.equalsIgnoreCase("S")
&& compChoice.equalsIgnoreCase("P"))
{
System.out.println("User Wins");
} else
{
System.out.println("User Loses");
}
System.out.print(
"Do you want to play again? (Y/N)");
playAgain = sc.nextLine();
} while (playAgain.equalsIgnoreCase("Y"));
System.out.println("Thanks for Playing!");
}
}

It looks like you forgot one do for your inner do while loop.
It should be :
do {
do {
System.out.println("Welcome to Rock, Paper, Scissors Game.");
System.out.println("Pick R, P, or S.");
userChoice = sc.nextLine();
} while (!userChoice.equalsIgnoreCase("P") && !userChoice.equalsIgnoreCase("R") && !userChoice.equalsIgnoreCase("S"));
...
} while (playAgain.equalsIgnoreCase("Y"));
Without that inner do (and the curly braces surrounding that loop's body), the inner loop becomes a while loop with an empty body.

Like Eran said, you need to wrap your do-while loop in another loop, that will keep asking user for correct input. This is fully working code. One thing that could be better is the message after user inputs wrong letter.
Edit: also make sure you draw random number for every iteration.
Edit 2: to change the message depending on user input you can introduce a new variable that will keep the track of number of times you asked user for correct input. If it is 0- it means user is asked the first time and we should print "Welcome" message. It is anything other than 0- you need to ask the user for correct input. After every round we assign zero to the variable again and the cycle repeats. I have implemented this change in the code. Note that this variable can also be a boolean.
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String userChoice;
String playAgain;
int iterationNumber;
while (true) {
iterationNumber = 0;
do {
if (iterationNumber == 0) {
System.out.println("Welcome to Rock, Paper, Scissors Game.");
System.out.println("Pick R, P, or S.");
} else {
System.out.println("Please enter valid letter.");
System.out.println("Pick R, P, or S.");
}
iterationNumber++;
userChoice = sc.nextLine();
} while (!userChoice.equalsIgnoreCase("P")
&& !userChoice.equalsIgnoreCase("R")
&& !userChoice.equalsIgnoreCase("S"));
String compChoice = "";
int randNum = (int) (Math.random() * 3);
switch (randNum) {
case 0:
compChoice = "R";
break;
case 1:
compChoice = "P";
break;
case 2:
compChoice = "S";
break;
}
System.out.println("The computer entered \"" + compChoice + "\".");
if (compChoice.equalsIgnoreCase(userChoice)) {
System.out.println("Draw");
} else if (userChoice.equalsIgnoreCase("R")
&& compChoice.equalsIgnoreCase("S")
|| userChoice.equalsIgnoreCase("P")
&& compChoice.equalsIgnoreCase("R")
|| userChoice.equalsIgnoreCase("S")
&& compChoice.equalsIgnoreCase("P")) {
System.out.println("User Wins");
} else {
System.out.println("User Loses");
}
System.out.print(
"Do you want to play again? (Y/N)");
playAgain = sc.nextLine();
if (playAgain.equalsIgnoreCase("N")) {
break;
}
iterationNumber = 0;
}
System.out.println("Thanks for Playing!");
}

Rerun main method if an invalid response is given?

So I made this rock paper scissors game a while ago using Java and I found a little bug I forgot to fix when I showed it to my friend today. Basically, the code takes a user input (i.e rock, paper, or scissors) and if their input does not equal rock, paper, or scissors, the main while loop is broken and the game is stopped.
How can I make it so that not only does it break the loop, but restarts it as well? I want to do this so that when someone gives an invalid input it automatically restarts so the player doesn't need to run the program all over again.
Here's the code for my main class:
public class rps {
public static void main(String []args){
boolean gameRunning = true;
while(gameRunning) {
System.out.println("Do you choose rock, paper, or scissors?");
UserChoice userInput = new UserChoice();
String userChoice = userInput.userDecide();
if(userChoice != "rock" || userChoice != "paper" || userChoice != "scissors") {
System.out.println("'" + userChoice + "'" + " is not a valid choice.");
System.out.println("Please choose between rock, paper, or scissors.");
gameRunning = false;
break;
// this is where I want to restart the function
}
System.out.println("You threw: " + userChoice);
ComputerInput computerChoice = new ComputerInput();
String computerInput = computerChoice.computerDecide();
System.out.println("Computer threw: " + computerInput);
CompareChoices compareResults = new CompareChoices();
gameRunning = compareResults.compare(userChoice, computerInput);
}
}
};
UPDATE
I figured out a few of the problems thanks to some help from the nice people on here. I used && instead of || (which is dumb because I originally used && anyways -_-), I used the "continue" statement instead of break, I removed gameRunning = false;, and I changed the way userChoice was compared to the valid responses.
Instead of comparing it to Strings like "rock" and "paper", I created an array
(String validChoices[] = {"rock", "paper", "scissors"};) which holds the valid responses. Then I compared userChoice to the indices of the array.
Here is my new code:
public class rps {
public static void main(String []args){
boolean gameRunning = true;
while(gameRunning) {
System.out.println("Do you choose rock, paper, or scissors?");
UserChoice userInput = new UserChoice();
String userChoice = userInput.userDecide();
String validChoices[] = {"rock", "paper", "scissors"};
if(!userChoice.equals(validChoices[0]) && !userChoice.equals(validChoices[1]) && !userChoice.equals(validChoices[2])) {
System.out.println("'" + userChoice + "'" + " is not a valid choice.");
System.out.println("Please choose either rock, paper, or scissors.");
continue;
}
System.out.println("You threw: " + userChoice);
ComputerInput computerChoice = new ComputerInput();
String computerInput = computerChoice.computerDecide();
System.out.println("Computer threw: " + computerInput);
CompareChoices compareResults = new CompareChoices();
gameRunning = compareResults.compare(userChoice, computerInput);
}
}
};
Thanks everyone!

Do not set gameRunning to false, to not use break, use continue, which will ignore the rest of the loop and start the loop again.
https://docs.oracle.com/javase/tutorial/java/nutsandbolts/branch.html

A couple of problems. setting your loop condition to false and breaking leaves no way to restart the loop. Also, as #resueman hinted at. Use .equals() instead of == for comparing strings. My suggestion is to put the error checking inside another while loop.
while(!userChoice.equals("rock") && !userChoice.equals("paper") && !userChoice.equals("scissors")) {
System.out.println("Your choice was invalid, try again");
userChoice = userInput.userDecide();
}
Also, you should maybe declare some of this stuff outside your while loop (I am thinking of your ComputerInput, UserInput and CompareChoices objects).

How to compare a String with an integer?

How can I compare a string with an int? I am making a Rock-paper-scissors game and how do I turn the string the user enters in to a int so the program can check who had won? Such as if the users enters "rock" the program registers that as 0 and so on?
package rpc;
import java.util.Random;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
/* Random number generator */
Random random = new Random();
/* Scanner object for input */
Scanner scanner = new Scanner(System.in);
/*
* Integer variables to hold the user and computer choice.
* 0 = Rock
* 1 = Paper
* 2 = Scissors
*/
String userChoice;
int computerChoice;
// Showing prompt and user input
System.out.println("Enter move (0 = Rock; 1 = Paper; 2 = Scissors):");
userChoice = scanner.nextLine();
// Checking if userChoice is 0, 1, or 2.
if (!userChoice.equalsIgnoreCase("Scissors") && !userChoice.equalsIgnoreCase("Paper")
&& !userChoice.equalsIgnoreCase("rock")) {
System.out.println("Invalid choice. Ending program.");
// Exit program
Main.main(args);
}
// Generating random computer choice
computerChoice = random.nextInt(3);
// Determining the winner
// If the choices are equal, it's a tie.
if (userChoice == computerChoice) {
if (userChoice == 0) {
System.out.println("Both players chose rock!");
} else if (userChoice == 1) {
System.out.println("Both players chose paper!");
} else {
System.out.println("Both players chose scissors!");
}
// Exit program
System.exit(0);
}
if (userChoice == 0) { // User chooses rock
if (computerChoice == 1) {
System.out.println("You chose rock; Computer chose paper");
System.out.println("Computer wins!");
} else {
System.out.println("You chose rock; Computer chose scissors");
System.out.println("You win!");
}
} else if (userChoice == 1) { // User chooses paper
if (computerChoice == 0) {
System.out.println("You chose paper; Computer chose rock");
System.out.println("You win!");
} else {
System.out.println("You chose paper; Computer chose scissors");
System.out.println("Computer wins!");
}
} else { // User chooses scissors
if (computerChoice == 0) {
System.out.println("You chose scissors; Computer chose rock");
System.out.println("Computer wins!");
} else {
System.out.println("You chose scissors; Computer chose paper");
System.out.println("You win!");
}
}
scanner.close();
}
}

You could use an enum to enumerate the three possible choices:
enum Hand {
ROCK,
PAPER,
SCISSORS;
public static Hand from(String input) {
for (Hand hand : values()) {
if (hand.name().equalsIgnoreCase(input)) {
return hand;
}
}
throw new IllegalArgumentException("Invalid choice: " + input);
}
}
Enums have an intrinsic integer value (that corresponds to the position they were defined at). ROCK.ordinal() will return 0, for example.

Just use pareseInt and convert string to int
For ex :
if(Integer.parseInt(userChoice) == computerChoice)
Make sure that the inputs are not null and formattable to int
edit : change parese to parse

Retrieving a random item from ArrayList
This is not the exact answer to your question (Integer.parseInt(myInt)) but you could try something more readable like this, avoiding the use of unnecessary Integers. And simplifies your code
Generate your arrayList and then pick the random "computer" choice.
List<String> posibilities = Arrays.asList("rock","paper","scissors");
String computerChoice = possibilites.get(Math.random(3));
then do your comparaison ;)
/* Chose the possibilities */
List<String> posibilities = Arrays.asList("rock","paper","scissors");
/* Scanner object for input */
Scanner scanner = new Scanner(System.in);
// Showing prompt and user input
System.out.println("Enter move (0 = Rock; 1 = Paper; 2 = Scissors):");
String userChoice = scanner.nextLine();
userChoice = possibilities.get(Integer.parseInt(userChoice));
// Checking if userChoice is 0, 1, or 2.
if(!possibilities.contains(userChoice)) {
System.out.println("Invalid choice. Ending program.");
// Exit program
Main.main(args);
}
// Generating random computer choice
String computerChoice = possibilites.get(Math.random(3));
// Determining the winner
// If the choices are equal, it's a tie.
if(userChoice.equals(computerChoice)) {
System.out.println("Both players chose " + userChoice);
// Exit program
System.exit(0);
}
System.out.println("You chose " + userChoice + "; Computer chose " + computerChoice);
if(userChoice.equals("rock")) { // User chooses rock
if(computerChoice.equals("paper")) {
System.out.println("Computer wins!");
} else {
System.out.println("You win!");
}
}
else if(userChoice.equals("paper")) { // User chooses paper
if(computerChoice.equals("rock")) {
System.out.println("You win!");
} else {
System.out.println("Computer wins!");
}
} else { // User chooses scissors
if(computerChoice.equals("Scissors")) {
System.out.println("Computer wins!");
} else {
System.out.println("You win!");
}
}
scanner.close();